Next you have a couple options(Doesn't matter which option you go with):

A) Put the replacement hard drive in the external enclosure. Boot up your laptop and use Disk Utility to format the new drive, then use SuperDuper to clone your old hard drive to your new hard drive. Finally, take the new hard drive and follow the guide to put it in your laptop.

Or

B) Use the guide to put the new hard drive in your laptop and put your old hard drive in the external enclosure. Boot your laptop from the old hard drive and use Disk Utility to format the new drive. Then use SuperDuper to clone the old hard drive to the new hard drive.

Then you should be good to go. Hope that helps!

Also, check out our HD-Software Install Guide. Option 2 will go into detail about using SuperDuper to clone your old hard drive to your new hard drive.